[time-nuts] TubeSat Personal Satellite Kit

[Lux, Jim (337C)]

On 8/5/09 10:31 PM, "Hal Murray" <hmurray at megapathdsl.net> wrote:

> 
> 
>> It used to be that you could make your payload as ballast for almost
>> free (that's how the early Amateur radio sats were launched).  But
>> now, the launch service providers know that folks are willing to pay.
>> The ³small sat² business has been so successful that most amateur
>> operations have been priced out of the market. A university with an
>> aerospace engineering program could easily afford $100-200K for launch
>> costs, which isn¹t much, spread across a couple dozen class members.
>> (For context, an introductory molecular biology class could cost
>> $6-10K just for reagents, gels, etc, to do simple gene splicing and
>> sequencing)
> 
> So what do areospace class projects actually do?  I assume they measure
> something.  What is left that is still interesting to measure?  What is the
> downlink like?  Is there an uplink?  (if nothing else, it would be handy to
> say "now" to the downlink.)
> 
> $100-200K over a "couple dozen class members" is still a big chunk of cash.
> Even at fancy text book prices that would buy a lot of books.   How much
> NSF/NASA/whatever funding is available?
> 

We're sort of straying from time-nuts here, although at least one cube sat I
am aware of (being built by Stanford and JPL) is obsessing about close in
phase noise. They're demonstrating a new design for a low power, small,
lightweight radio science transponder. Receives a signal at around 7.1 GHz
and coherently synthesizes a transmitted signal at around 8.4 GHz.
Comparing the phase of the signal from the ground with the received signal
lets you do very (very) precise measurements of the light time to and from
the spacecraft. (This is how we know the velocity of a spacecraft at Saturn
to a few mm/s, which lets you figure out things like the internal structure
of a planetary body, by looking at the gravity field.  It also can be used
for things like occultations to look at the atmosphere(s) and to study rf
propagation in interplanetary space.)

But, returning to your questions..
Is there stuff interesting to measure?  Sure. A few years back, I worked on
a project that measured the 3D current flow in the aurora, using small
probes ejected from a sounding rocket over Alaska.  There's all manner of
interesting stuff to do.

Is there a command link? Sometimes yes, sometimes no. Depends on the
spacecraft and whether you want to burn the mass and power for a receiver.
Sputnik had no uplink.  I keep threatening my friends to put up Jim-Sat,
that radiates an inspirational message along the lines of "Jim Lux is a cool
dude" until it dies.  A more time-nuts-y idea might be to fly a bunch of
oscillators in different orientations with close frequencies (so you don't
have much bandwidth requirement) and look at the relative changes. Maybe
those real inexpensive SiTime MEMS resonators.  It would just be a beacon,
and you'd record data until it died.

This is an example of a "flight validation" experiment. Maybe you have a
kind of technology or a component design that has never flown in space, and
by doing an inexpensive experiment like this, you can achieve the holy grail
of (Technology Readiness Level) TRL 7, opening the door to using that
technology on a future spacecraft, with a perception of reduced risk. (Mind
you, you will have to fight the "well a $50k launch and 3 weeks isn't real
space flight, like sending it to Mars" thing..)


But even if there's not "new science" from such a class project, there is
the practical experience of having had to actually do the development and
build the spacecraft. You'll have to put it on the shaker table and have it
fall apart. You'll have to run through thermal vacuum testing and discover
that those parts get too hot or too cold, and what worked fine on the bench
stops working when one side is at +60 and the other at -30. To put it in the
horrible commercial terms that universities now seem to use, it increases
the future revenue potential of the student, raising the ROI on their
investment in education.  (*I* think you should get an education because
it's interesting.  It's an inefficient way to make money and a poor
investment in financial terms, but leads to other philosophical problems.)
But realistically, I'd much rather hire someone who's done this kind of
project than someone who has just fooled with some eval boards in lab.

As for the expense. There's a lot of expenses in having a student in class
beyond the text books.  If you take chemistry, someone has to provided the
chemicals, even you have to buy your own glassware. In biology, there's lab
specimens, etc.  Not to mention substantial equipment costs (keeping a SEM
up and running isn't free, and it's a deal compared to something like a DNA
sequencing box.)  Spread the $200K of a class project across couple years
and 20 people, and it's $5k/year/student, which isn't much.  The labor costs
for the staff are bigger.

Jim